JPS61248447A - Formation of wiring layer - Google Patents

Abstract

PURPOSE:To improve the adhesiveness of a wiring layer by a method wherein the first tungsten silicide WSix film is formed by a vapor phase deposition and subjected to a heat treatment and the second WSix film is formed by a vapor phase deposition to form WSix film with a predetermined film thickness. CONSTITUTION:After a polycrystalline Si film 5-1 is deposited by a CVD method, the first WSix film 5-2 with a film thickness of 1,000Angstrom is deposited by a CVD method. When the film 5-1 and the film 5-2 are subjected to a heat treatment in a neutral or reducing atmosphere at a certain temperature for a certain period, a reaction is created between the film 5-1 and the film 5-2 to form an alloy and the Si content in the film 5-2 is increased. Further, the second WSix film 5-3 is deposited by a CVD method to form a WSix film with a rich tungsten content. With this constitution, the variation of the material composition in the wiring layer is such that the Si content decreases and the tungsten content increases from the bottom layer to the top layer and the adhesiveness of the wiring layer is improved.

Description

[Detailed Description of the Invention] Mouth! % cotungsten silicide film is grown in a vapor phase, then heat treated at high temperature, and a tungsten silicide film is again grown in a vapor phase thereon.

[Industrial Application Field] The present invention relates to a method for forming a wiring layer in a semiconductor device.

In a semiconductor device such as an RC, semiconductor elements and other circuit elements are formed on a semiconductor substrate, and a large number of electrode wirings leading out from these areas are provided on the upper surface.

Up until now, aluminum films or aluminum alloy films have been used for these electrode wirings, but the problem with aluminum is its low melting point, which makes it difficult to form multilayer wiring by increasing the integration and density of ICs. However, there are drawbacks that limit the formation of the glabella insulating film.

Therefore, as an alternative wiring material, a method has recently been adopted in which high-melting point metal silicide, which has better electrical conductivity than conductive polycrystalline silicon film, is used for electrode wiring. Among these, tungsten silicide (WSix) film is This is a typical silicide film.

However, sufficient consideration must be given to the adhesion of this tungsten silicide film.

[Prior Art] Fig. 2 shows a partial cross-sectional view of a wiring layer in a semiconductor device such as an IC, in which 1 is a silicon substrate 52 as a wiring layer, 3 is silicon dioxide (Si02) It', and the wiring N2 is a polycrystalline layer. Silicon film 2-1 and tungsten silicide film 2
-2. The reason why the polycrystalline silicon film 2-1 is interposed in this way is that if the metal silicide film is brought into direct contact with the silicon substrate, there is a risk that the metal will diffuse into the silicon substrate and the device characteristics will be impaired.

Conventionally, the method of forming this tungsten silicide film 2-2 has been chemical vapor deposition (CVD).
4) is deposited by thermal decomposition, and the reaction formula is as shown below.

WF6 +SiH4-WSix +HFHere, the X value of tungsten silicide (WSix) takes a value from about 2 to 4, and the larger the X value, the more silicon (Si)
This results in a tungsten silicide film with a large amount. Moreover, this X value can be changed by changing the thermal decomposition temperature, and the third
The figure is a diagram showing this. The graph shows that the vertical axis is the X value and the horizontal axis is the thermal decomposition temperature, and the higher the thermal decomposition temperature, the larger the X value and the larger the amount of silicon.

However, by lowering the thermal decomposition temperature, W Si x
If the X value of
There is a problem in that the tungsten silicide film and the polycrystalline silicon film are peeled off due to the annealing (p!!: treatment). Annealing is also necessary for crystallization and silicidation of the grown film, and is unavoidable. especially,
When a phosphorous silicate glass (PSG) film is deposited as an insulating film between wiring layers or a coating film on a wiring layer, the tungsten silicide film containing a small amount of silicon is easily peeled off.

On the other hand, forming a tungsten silicide film with a large amount of tungsten and a small amount of silicon forms a low-resistance, high-conductivity wiring layer, which has the advantage of helping improve IC performance. It is.

The present invention solves these problems and proposes a method for forming a wiring layer containing a tungsten silicide film with a large amount of tungsten (lynch) that does not peel off even during annealing.

[Means for solving the problem] The purpose is to grow a tungsten silicide film in a vapor phase,
Next, after heat-treating the tungsten silicide film,
This is achieved by a method of forming a wiring layer in which a second tungsten silicide film is vapor-phase grown on the tungsten silicide film to form a tungsten silicide film with a predetermined thickness.

[Operation] That is, in the present invention, when a tungsten silicide film is grown by chemical vapor deposition, a high-temperature heat treatment step is sandwiched between the two to form a wiring layer made of the tungsten silicide film.

[Example] Hereinafter, embodiments will be described in detail with reference to the drawings.

FIG. 1 shows a partial cross-sectional view of a wiring layer according to the present invention. It is a three-layer composite layer consisting of -3. In addition, other symbols are the same as those in FIG. 2 and are given the same symbols.

In order to form the wiring layer 5 in this way, first, a film thickness of 2
After a polycrystalline silicon film 5-1 having a thickness of about 1.000 μm is grown by the CVD method, a first tungsten silicide film 5-2 having a thickness of 1.000 μm is similarly grown by the CVD method. To do this, for example, the reaction chamber of the CVD apparatus is heated to a constant temperature of 350°C, and wF6 gas using helium (He) as a carrier gas and S gas using He as a carrier gas are prepared.
iH4 gas is introduced to thermally decompose the WF gas and the Si2H6 gas, thereby growing a tungsten silicide film 5-2. Then, the tungsten silicide film becomes W
A tungsten film with a thickness of about Six (X-2,2) grows.

Next, heat treatment is performed at a temperature of 800"C for several tens of minutes in a neutral or reducing atmosphere. Then, the polycrystalline silicon film 5-1 and the first tungsten silicide film 5-2 react and become alloyed. tungsten silicide film 5
-2 silicon amount increases.

Thereafter, a second tungsten silicide II*5-3 is grown to a thickness of 1,000 by the same CVD method. The conditions are the same as above, and the gas flow rate is, for example, WF
6 gas at 2 cc/min and SiH4 gas at 120 cc/min.

Then, the second tungsten silicide film is also a tungsten-rich grown film, and both tungsten silicide films become tungsten-rich tungsten silicide films of approximately WSix (X=2 to 2°2). Further, this wiring layer has a component in which the amount of silicon decreases and the amount of tungsten increases from the lower layer to the upper layer, and the wiring layer having such a composition has good adhesion.

Therefore, according to the method for forming a wiring layer according to the present invention, a high-quality wiring layer having good adhesion and high conductivity can be obtained.

[Effects of the Invention] As is clear from the above description, according to the present invention, a tungsten glue/notch wiring layer with good adhesion is formed, and an I
This is useful for improving the performance of C.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a wiring layer according to the present invention, FIG. 2 is a sectional view of a conventional wiring layer, and FIG. 3 is a graph showing the relationship between thermal decomposition temperature and X value of W S i x. In the figure, 1 is a silicon substrate, 3 is a 5i02 film, 2.5 is a wiring layer, 2-1.5-1 is a polycrystalline silicon film, and 2-2.5-2.5-3 is a tungsten silicide film. ing. O→My old ear's position C kalpa (Everyone is Heiju, Men's 1st picture, sparrow bundle, Tokoro (narrow λ [no!'l'r Men's nail 2nd figure g + solution * Z X t v / ) rlI f'1-r
l to lWk 3 figure

Claims (1)

[Claims] After growing a tungsten silicide film in a vapor phase, and then heat-treating the tungsten silicide film, a second tungsten silicide film is grown in a vapor phase on the tungsten silicide film to form a tungsten silicide film with a predetermined thickness. A method for forming a wiring layer, characterized in that: